Fetal antigens in human digestive tumors

Abstract

CANCER of the digestive organs ranks first as the leading cause of cancer mortality [l]. Immunology may help the physician by providing new diagnostic and therapeutic facilities. Detection of tumor-associated antigens in serum or biological fluids, or the demonstration of immunologic responses in host-tumor systems could simplify and advance the diagnosis of digestive malignancies and improve the results of curative treatment. Ideally, an immunologic test should be simple, safe and reliable enough to be used as a mass screening method in determining a Ihigh risk population. More sophisticated methods (radiography, endosCOPY, * .) could then be employed to confirm the presence and localization of the tumor. In patients with proven digestive cancer, immunologic tests may still be useful in evaluating the prognosis or monitoring the effects of treatment. With a few exceptions, surgery is the one curative therapy for digestive malignancies. Its results are limited however by the extension of the tumor. Palliative radiotherapy and chemotherapy are usually disappointing. Therefore an immunological treatment, if it was possible, could be very helpful in destroying residual tumor tissue not removed by surgery. Immunodiagnosis and immunotherapy are only possible if antigenic difference does exist between the tumor and the corresponding normal digestive tissue. These tumor-associated antigens could be valuable for clinical purposes according to the;., specificity, immunogenicity and their possible restriction to individual tumors. The specificity of tumor-associated antigens can be qualitative, if the antigen is completely absent from the non-cancerous tissues. This qualitative tumor-specificity is always questionable, as more sensitive techniques could be able to demonstrate minute amounts of antigens in non-cancerous tissues. For most of the carcino-fetal antigens, the specificity is only quantitative: the antigenic concentration is stronger in cancerous than in non-cancerous tissues. The immunogenicity of the tumor-associated antigen for the cancer-bearing patient is an important factor, as it is the required condition for immunotherapy. Immunogenicity depends, in part, on the specificity of the antigen. However, an immune reaction can be produced against quantitatively tumor-specific, or even normal antigens. In experimental systems, tumor-associated antigens can be characteristic of an individual tumor: i.e. cancer induced by chemical agents have individual antigens, detected by transplantation methods, which are different from one tumor to another (even if induced in the same organ by the same carcinogen); virus induced tumors, in contradiction, share common antigens. In human cancer, the practical use of tumor-associated antigens will be fundamentally different if they are common to a group of tumors, or restricted to an individual cancer. Private antigens could only be detected by autochtonous reactions. Common antigens could be identified by reagents raised against other tumors of the same group. Among the antigens associated with human digestive malignancies, the carcino-fetal antigens are of special importance. Between 1965 and 1966, relationships were demonstrated